The pg_logicalinspect module provides SQL functions that allow you to inspect the contents of logical decoding components. It allows the inspection of serialized logical snapshots of a running PostgreSQL database cluster, which is useful for debugging or educational purposes.
By default, use of these functions is restricted to superusers and members of the pg_read_server_files role. Access may be granted by superusers to others using GRANT.
pg_get_logical_snapshot_meta(filename text) returns record #Gets logical snapshot metadata about a snapshot file that is located in the server's pg_logical/snapshots directory. The filename argument represents the snapshot file name. For example:
postgres=# SELECT * FROM pg_ls_logicalsnapdir();
-[ RECORD 1 ]+-----------------------
name | 0-40796E18.snap
size | 152
modification | 2024-08-14 16:36:32+00
postgres=# SELECT * FROM pg_get_logical_snapshot_meta('0-40796E18.snap');
-[ RECORD 1 ]--------
magic | 1369563137
checksum | 1028045905
version | 6
postgres=# SELECT ss.name, meta.* FROM pg_ls_logicalsnapdir() AS ss,
pg_get_logical_snapshot_meta(ss.name) AS meta;
-[ RECORD 1 ]-------------
name | 0-40796E18.snap
magic | 1369563137
checksum | 1028045905
version | 6
If filename does not match a snapshot file, the function raises an error.
pg_get_logical_snapshot_info(filename text) returns record #Gets logical snapshot information about a snapshot file that is located in the server's pg_logical/snapshots directory. The filename argument represents the snapshot file name. For example:
postgres=# SELECT * FROM pg_ls_logicalsnapdir();
-[ RECORD 1 ]+-----------------------
name | 0-40796E18.snap
size | 152
modification | 2024-08-14 16:36:32+00
postgres=# SELECT * FROM pg_get_logical_snapshot_info('0-40796E18.snap');
-[ RECORD 1 ]------------+-----------
state | consistent
xmin | 751
xmax | 751
start_decoding_at | 0/40796AF8
two_phase_at | 0/40796AF8
initial_xmin_horizon | 0
building_full_snapshot | f
in_slot_creation | f
last_serialized_snapshot | 0/0
next_phase_at | 0
committed_count | 0
committed_xip |
catchange_count | 2
catchange_xip | {751,752}
postgres=# SELECT ss.name, info.* FROM pg_ls_logicalsnapdir() AS ss,
pg_get_logical_snapshot_info(ss.name) AS info;
-[ RECORD 1 ]------------+----------------
name | 0-40796E18.snap
state | consistent
xmin | 751
xmax | 751
start_decoding_at | 0/40796AF8
two_phase_at | 0/40796AF8
initial_xmin_horizon | 0
building_full_snapshot | f
in_slot_creation | f
last_serialized_snapshot | 0/0
next_phase_at | 0
committed_count | 0
committed_xip |
catchange_count | 2
catchange_xip | {751,752}
If filename does not match a snapshot file, the function raises an error.
Bertrand Drouvot <[email protected]>
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